Tyre changing machine

Abstract

A tyre changing machine includes a wheel support assembly for locking and setting in rotation a rim of a wheel from which to demount or on which to mount a tyre, and a bead breaking tool disposed at an end of a bead breaking arm and able to carry out the bead breaking operation. The bead breaking arm is movable between a disengaged position and a working position. A motor device has an output drive shaft for moving the bead breaking arm between the disengaged and working positions. Means for transmitting the drive from the motor device to the bead breaking arm include threaded means having an external screw-thread and hollow counter-threaded means operatively coupled with the threaded means. Connecting means operatively associate the means for transmitting the drive to the bead breaking arm.

Claims

1. A tyre changing machine comprising a frame restable on a rest surface; a wheel support assembly for locking and setting a rim of a wheel in rotation from which to demount or on which to mount a respective tyre, said wheel support assembly being mounted on the frame; a bead breaking arm having a first end connected to the frame; a bead breaking tool connected to a second end of said bead breaking arm and able to carry out the bead breaking operation of the tyre; the bead breaking arm being movable between a disengaged position, in which the bead breaking tool is distanced with respect to the tyre of the wheel to be debeaded, and a working position, wherein said bead breaking tool can engage on said tyre; an electric motor having a rotating output drive shaft for moving the bead breaking arm between the disengaged position and the working position and vice versa, means for transmitting drive from the electric motor to the bead breaking arm, said means for transmitting the drive comprising a rod element having an externally screw-threaded first portion, and a tubular body having an internally screw-threaded portion threadingly coupled with the first portion of the rod element; and connecting means for operatively connecting the rod element to the bead breaking arm, wherein said connecting means are adapted to slidably engage the rod element, wherein the tubular body is operatively coupled to the rotating output drive shaft of the electric motor such that rotation of the output drive shaft causes rotation of the tubular body, to move the rod element axially relative to the tubular body and the bead breaking arm from the disengaged position to the working position and vice versa, and wherein said means for transmitting the drive further comprise a striker element adapted to engage with at least one of the connecting means and the bead breaking arm.

2. The tyre changing machine according to claim 1, wherein the connecting means engage a non-threaded second portion of the rod element abutting the first portion of the rod element.

3. The tyre changing machine according to claim 2, wherein the connecting means comprise a sleeve-profiled element for engaging the second portion of the rod element.

4. The tyre changing machine according to claim 2, wherein the connecting means comprise an element having a grooved profile for engaging the second portion of the rod element.

5. The tyre changing machine according to claim 2, wherein the striker element is mounted on the second portion of the rod element.

6. The tyre changing machine according to claim 1, wherein the connecting means are hinged, by means of at least a pin, to the bead breaking arm.

7. The tyre changing machine according to claim 6, wherein the at least a pin is adapted to engage in a respective slot fashioned in the bead breaking arm.

8. The tyre changing machine according to claim 1, wherein the connecting means are hinged, by at least a first pin, to an intermediate connecting element, said intermediate connecting element being hinged, by means of at least a second pin, to the bead breaking arm.

9. The tyre changing machine according to claim 1, comprising means for selectively transmitting the drive from the electric motor to the bead breaking arm or to the wheel support assembly and able to selectively activate said bead breaking arm or said wheel support assembly.

10. The tyre changing machine according to claim 9, wherein the means for selectively transmitting the drive from the electric motor to the bead breaking arm or to the wheel support assembly comprise: a drive selector device mounted on the drive shaft; first drive transmission means mounted on the drive shaft and adapted to transmit the drive to the wheel support assembly; second drive transmission means mounted on the drive shaft and adapted to transmit the drive to the bead breaking arm; and wherein the drive selector device is able to be removably coupled to the first or the second drive transmission means.

11. The tyre changing machine according to claim 10, comprising: control means, activatable by an operator, for activating the bead breaking arm; a control rod having a first and a second ends and connected, at the first end, to the drive selector device and, at the second end, to a control and stop element associated to the means for transmitting drive from the electric motor to the bead breaking arm; a flexible control member, activatable by the control means and operatively connected to the control rod, for coupling the drive selector device to the first and/or second drive transmission means and for displacing the control and stop element from a rest position, in which said control and stop element is in a distal position with respect to the means for transmitting drive from the electric motor to the bead breaking arm, to an operating position, in which said control and stop element is in a proximal position with respect to the means for transmitting drive from the electric motor to the bead breaking arm.

12. The tyre changing machine according to claim 11, wherein the control means comprise a lever mounted on the bead breaking arm in proximity of the bead breaking tool.

13. The tyre changing machine according to claim 1, wherein the rod element comprises a non-threaded second portion abutting the first portion of the rod element.

14. The tyre changing machine according to claim 13, wherein the first portion of the rod element is proximal the frame and the second portion of the rod element is proximal the bead breaking tool.

15. The tyre changing machine according to claim 13, wherein the rod element performs a purely translational movement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of some preferred, but not exclusive, embodiments of a tyre changing machine according to the present invention will appear more clearly from the detailed description.

(2) This description will be explained below with reference to the attached drawings, provided solely for indicative and therefore non-limiting purposes, in which:

(3) FIG. 1 shows a schematic axonometric view of a tyre changing machine according to the present invention, provided with a bead breaking assembly with a paddle-shaped bead breaking tool and a wheel mounted on the wheel support assembly;

(4) FIG. 2 illustrates the machine of FIG. 1, in an axonometric view but on an opposite side and with the lateral casing partly removed;

(5) FIG. 3 illustrates a tyre changing machine according to the present invention, in a view from above and with lateral casings partially removed, in the configuration in which the bead breaking arm is in the disengaged position, i.e. distanced from the machine frame;

(6) FIG. 4 illustrates the tyre changing machine of FIG. 3, with the bead breaking arm in the working position, i.e. neared to the machine frame;

(7) FIG. 5 is an axonometric view of a bead breaking assembly according to the present invention;

(8) FIG. 6 is an axonometric view of section of a detail of the bead breaking assembly according to the present invention;

(9) FIGS. 7a, 7b, 7c, 7d, 7e illustrate constructional details and views by way of example of the bead breaking assembly of the present invention, when the bead breaking arm is in the decoupled configuration from the motor device and in the disengaged position;

(10) FIGS. 8a, 8b, 8c, 8d, 8e illustrate constructional details and views by way of example of the bead breaking assembly of the present invention, when the bead breaking arm is in the coupled configuration to the motor device and in the disengaged position;

(11) FIG. 8f is a partially sectioned view of a constructional detail of the bead breaking assembly of the present invention, when the bead breaking arm is in the coupled configuration to the motor device and in an intermediate position between the disengaged position and the working position;

(12) FIGS. 9a, 9b, 9c illustrate constructional details and views by way of example of the bead breaking assembly of the present invention, when the bead breaking arm is in the coupled configuration to the motor device and in the working position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(13) In the description that follows, any expressions used, for example “right”, “left”, “above”, “below”, “upper”, “lower” and the like, have a merely illustrative aim and refer to the particular arrangement of the elements present in the accompanying figures, and therefore have no limiting characteristics.

(14) With reference to FIG. 1, the tyre changing machine 1 comprises a frame 2 restable on a support surface or plane A, generally horizontal.

(15) The frame 2 of the tyre changing machine 1 supports an upright or support post 3 having a vertical extension, adapted to support means 4 for mounting/demounting a tyre P to/from a respective rim C of a wheel R. The means 4 for mounting/demounting comprise at least a mounting/demounting tool 5, of known type, for example having a lever, hook or the like. The mounting/demounting means 4 can further comprise a plurality of accessories, also of known type, for example a bead presser or the like, not shown in the figures.

(16) The tyre changing machine 1 illustrated in FIG. 1 further comprises a wheel support assembly 6, mounted vertically on the frame 2, for locking and rotating a rim C of a wheel R about a central axis thereof.

(17) Such assembly 6 can be of various types, for example it can comprise a rotating plate provided with grips for hooking the rim C at the annular containing flanges thereof, or, as in the illustrated case in the figures, can be designed to lock the rim C at the central hole thereof, using appropriate locking means.

(18) A bead breaking arm 7 having a substantially horizontal longitudinal extension is associated, normally hinged to the frame 2 of the machine 1, about a rotation axis that is substantially vertical, at a first end thereof. The associating of the bead breaking arm 7 to the frame can be done directly or indirectly by means of, for example, an intermediate arm 7a, which can be solidly constrained to the frame 2 or associated movably with respect to the frame 2, for example, but not necessarily, hinged to the frame.

(19) The bead breaking arm 7 illustrated in FIG. 1 has a longitudinal extension that is substantially horizontal, though inclined by a few degrees upwards, so as to facilitate the bead breaking operations for wheels having large dimensions. By bead breaking arms having a longitudinal extension that is substantially horizontal are meant bead breaking arms having a longitudinal horizontal or inclined extension, in general though not necessarily upwards (i.e. on the opposite side with respect to the rest plane of the tyre changing machine), by a few degrees with respect to the horizontal plane, for example inclined by 25° with respect to the horizontal plane, preferably up to 15°. It is however possible, within the scope of the present invention, to have inclinations of the bead breaking arm that are different from those mentioned here purely by way of non-limiting example.

(20) The bead breaking arm 7, at a second end thereof, is provided with a bead breaking tool 8, for example having a blade shape, a paddle shape, a rotating disc shape, a roller shape or another shape. The bead breaking tool 8 interacts with the beads of the tyre P to carry out the bead breaking operation, i.e. for detaching said beads from the rim C, before the following actual demounting. In reference to FIG. 3, the bead breaking arm 7 is movable between a disengaged position, in which said bead breaking tool 8 is substantially distanced from the frame 2 and therefore with respect to the tyre P of the wheel R to be debeaded, and a working position, wherein said bead breaking tool 8 is closer to the frame 2 of the tyre changing machine 1, as illustrated in FIG. 4, and therefore can potentially engage on said tyre P. In regard to this, a substantially vertical opposing surface 9 is mounted on the frame 2 of the bead breaking tool 8 at the area of action of the tyre changing machine 1, against which opposing surface 9, in use, the wheel R is arranged with the tyre P to be debeaded, also vertically, i.e. with the central axis thereof arranged horizontally. The opposing surface 9 is adapted to cooperate with the bead breaking tool 8 so as to carry out the bead breaking operation of the tyre P. This opposing surface 9 is knurled so as to increase the coefficient of friction with the wheel R placed against it.

(21) The tyre changing machine 1 has one or more control pedals F for managing the functions thereof, for example for setting the support assembly 6 in rotation, for locking and/or for freeing the wheel on/from the support assembly 6, so as to activate the bead breaking arm 7, etc.

(22) The tyre changing machine 1 is provided with an electric motor 10, provided with an output drive shaft 10a.

(23) The electric motor 10 is used for transmitting drive to the wheel support assembly 6, generally for activating at least the rotation. In some cases, and with appropriate support assemblies, for example as illustrated in patent publication EP-A1-2639566, the electric motor 10 is adapted, in addition to setting the support assembly and possibly a rim mounted thereon in rotation, to activate the locking and/or release of the rim on/from the support assembly.

(24) In a preferred embodiment of the present invention, illustrated in FIG. 2, and in FIG. 5, the tyre changing machine 1 of the present invention has a single electric motor 10 for moving both the bead breaking arm 7 and the wheel support assembly 6. According to this embodiment, it is also present a means 11 for selectively transmitting the drive 11 from the electric motor 10 to the bead breaking arm 7 or to the wheel support assembly 6. Said means 11 can be activated by an operator, who can therefore choose, time by time, whether to use the electric motor 10 for activating the wheel support assembly 6 or the bead breaking arm 7.

(25) The bead breaking arm 7 can be provided, preferably in proximity of the bead breaking tool 8, with a control lever L. Said control lever L can advantageously control the electric motor 10 for activating the movement of the bead breaking arm as well as, eventually, in the context of the present preferred embodiment, also for controlling a drive selector device, as illustrated in the following.

(26) In FIG. 5, a part of the means 11 for selectively transmitting the drive from the electric motor 10 to the bead breaking arm 7 or to the wheel support assembly 6 is illustrated in greater detail. The electric motor 10 is provided with a drive shaft 10a (FIGS. 7c and 8c) on which a drive selector device 14 is mounted, and a first pulley 15 is mounted idle on the drive shaft 10a and is adapted to transmit the drive to the wheel support assembly 6; a second pulley 16 is also mounted idle on the drive shaft and is adapted to transmit drive to the bead breaking arm 7 of the bead breaking assembly associated to the tyre changing machine.

(27) Both the pulleys are supported on the drive shaft 10a by appropriate support elements, for example bearings, and retained in the seating by retaining means.

(28) A drive selector device 14 can be removably coupled to the first 15 or the second 16 pulley.

(29) Said removable coupling is preferably made in the following way.

(30) The drive selector device 14 comprises a selector element, preferably having a circular crown shape, which is mounted on the drive shaft 10a by a woodruff key coupling, i.e. with the use of grooved profiles. In this way, apart from a modicum of play, the drive selector device 14 cannot move radially with respect to the axis of the drive shaft 10a, however it is free to slide axially thereon. The selector element is moved by a control device, preferably fork-shaped, coupled to the selector element at a peripheral annular portion thereof, and is adapted to translate it axially along the drive shaft 10a, in order to enmesh the first 15 or second 16 pulley, according to the direction of the axial translation which is imparted thereon. The selector element can be of various types, for example having frontal enmeshing.

(31) The coupling between the selector element and each pulley 15, 16 is therefore temporary and reversible. In fact, as mentioned, said selector element can slide axially along the drive shaft 10a in response to a stress received from the fork-shaped control device, which in turn is activated by appropriate control means activatable by an operator. Such means can be connected to the control lever L associated to the bead breaking arm 7, or can be connected to various control means, for example to a second control lever distinct from the first lever L, or a pedal F, a button or the like, also in combination with each other.

(32) As illustrated in FIGS. 7 and 8a, the control means activatable by an operator can comprise a Bowden cable 12 connected to a movable block B, which can also have a cam shape, solidly constrained to the base of the lever L. By rotating the lever L in the clockwise direction, the Bowden cable 12 is pulled, which causes the decoupling of the drive selector device 14 from the first pulley 15 and the coupling thereof with the second pulley 16, so as to transmit drive to the bead breaking arm 7.

(33) The movable block B located at the base of the lever L can also be provided with a button device, for example of the microswitch type (not illustrated in the figures) which is activated by the rotation of the block B and which can be configured so as to send a switching-on command to the electric motor 10.

(34) The electric motor 10 can alternatively be activated by means of a button (not illustrated in the figures), for example located in proximity of the handle M of the lever L.

(35) Once the operator has chosen, for example using the lever L, whether to use the electric motor 10 for activating the wheel support assembly 6 or the bead breaking arm 7, the transmission of drive from the first pulley 15 to the wheel support assembly 6 or from the second pulley 16 to the bead breaking arm 7 is lastly realised using appropriate transmission belts.

(36) For example, a first belt 150 is preferably associated to the first pulley 15, which preferably has a trapezoidal shape, while a second belt 160 is preferably associated to the second pulley 16, preferably of a Poly-V type.

(37) With reference to FIG. 5, the Bowden cable 12 operatively connects the lever L to a control and stop element 13 having a shape of a connecting bracket, which is mounted at a first end of a control rod 17 connected at a second end thereof to the drive selector device 14.

(38) In this way, by acting on the lever L the control and stop element 13 displaces, which in turn displaces the drive selector device via the control rod 17.

(39) The control and stop element 13 is in turn connected to the means for transmitting drive from the electric motor 10 to the bead breaking arm 7, as illustrated in FIG. 6. The terminal part of the control and stop element 13 has a sleeve shape and extends about the rod element 18, where it is subjected to the action of the helical spring 19, associated to the rod element, and a pusher element 20, advantageously preloaded by elastic means 20a.

(40) The pusher element 20 further comprises an abutment surface 210 and a stem 220.

(41) The means for transmitting drive from the electric motor 10 to the bead breaking arm 7 comprise a pulley 21 mounted solidly to the tubular body 22 (FIGS. 7c and 8c), which is supported by means of appropriate bearings, for example of a type having conical rollers, by a support tube 23 solidal to the frame 2 of the tyre changing machine 1.

(42) The pulley 21 can be made in a single piece, for example by die casting, together with the tubular body 22, which single element can include appropriate abutments for blocking the support bearings in position.

(43) The pulley 21 can however be simply mounted solidly to the tubular body 22, for example by means of a keyed coupling or the like.

(44) The pulley 21 is set in rotation by the second transmission belt 160, preferably, even if not necessarily of the Poly-V type, associated to the second pulley 16, which is mounted on the drive shaft 10a. The rotation of the second pulley 16 then sets in rotation the pulley 21 and therefore also the tubular body 22.

(45) The tubular body 22 is internally hollow, and comprises at least a nut screw-shaped portion. The nut screw-shaped portion can be made with an endless screw 24 solidly fixed to the tubular body.

(46) The endless screw 24 is operatively coupled with a screw-shaped manoeuvring portion 18a of the rod element 18. The screw-shaped manoeuvring portion 18a is preferably of the trapezoidal screw type, and consequently the endless screw 24 is preferably of the trapezoidal type.

(47) The rotation of the tubular body 22 and of the endless screw 24 therefore set the rod element 18 in movement, which slides axially, in screwing and/or unscrewing direction, at least partially within the tubular body 22.

(48) In the axial movement thereof, the rod element 18, while remaining operatively connected to the endless screw 24, will generally be adapted at least partially to exit from the tubular body 22, so as to engage appropriate connecting means 25 (FIGS. 3, 4, 7b, 8b) associated to the bead breaking arm 7.

(49) The rod element 18 further comprises a second portion 18b, for example, but not necessarily, having an at least partially circular section, which is preferably smooth, i.e. does not have threads (FIGS. 7c and 8c).

(50) The tube 23 is provided with a flange 31 which, in addition to supporting the pusher element 20, interacts with the smooth portion 18b of the rod element 18, thus preventing an eventual rotation thereof and ensuring a movement of a purely translational type. The interaction of the flange 31 with the smooth portion 18b of the rod element 18 occurs by virtue of a shoulder 32 fashioned on the smooth portion 18b of the rod element 18 (FIGS. 7d, 7e, 8d, 8e).

(51) The presence of the shoulder 32 therefore defines two sub-portions internally of the smooth portion 18b of the rod element, a first sub-portion 321, upstream of the shoulder 32, has a circular transversal section having larger diameter with respect to a second sub-portion 322, situated downstream of the shoulder. In fact, the second sub-portion 322 will generally not have a proper circular section, but rather a section defined by an arc of circumference and a segment, at which the rod element actually has a flat surface 320.

(52) In fact, therefore, the flange 31 includes an advantageously complementarily-shaped through-hole, for enabling the second sub-portion 322 of the smooth portion 18b of the rod element 18 to engage with ease therein, with a free sliding coupling.

(53) In reference to FIG. 6, the first sub-portion 321 is located on the left, upstream of the shoulder 32, while the second sub-portion 322 is located on the right, i.e. downstream of the shoulder 32. The rod element exhibits at least the flat surface 320 at least at the second sub-portion 322.

(54) A washer 33, mounted on the rod element 18, protects the threaded portion 18a thereof from any eventual contact with the helical spring 19. The washer 33 can be mounted freely slidably on the rod element 18. In this case, it will be dimensioned in such a way as never to come into contact with the threaded portion 18a of the rod element 18, for example the washer 33 might have a larger diameter than the tubular body 22.

(55) Alternatively, the washer 33 might be mounted fixed on the rod element 18. As a further alternative, the function of protecting the threaded part 18a of the rod element 18 from a possible contact with the helical spring 19 might be carried out by an appropriate shoulder fashioned at the position of the last turn of the threaded portion 18a of the rod element 18.

(56) Said second smooth portion 18b of the rod element 18 is preferably destined to engage in the connecting means 25, which for example comprises a sleeve-shaped element, in which the smooth portion 18b of the rod element 18 can freely slide.

(57) The sleeve 25 preferably has a section alike to that of the second sub-portion 322 of the smooth portion 18b of the rod element.

(58) The sleeve is provided with a first and a second pins 26, 27 destined to engage in respective slots 28, 29 fashioned on the bead breaking arm 7. The two pins 26, 27 are preferably arranged along the same vertical axis. The two slots 28, 29 are fashioned on respective surfaces solidly constrained to the bead breaking arm, a first surface located in a distal position with respect to the rest plane A, and a second surface located in a proximal position with respect to said rest plane A.

(59) A striker element 30, for example a security nut preventing unscrewing with end-run functions, is preferably mounted to an end of the smooth portion 18b of the rod element 18 that is opposite with respect to the frame 2 of the machine 1 and in any case externally of the bead breaking arm 7 and the sleeve 25.

(60) The movement of the bead breaking arm 7 of the present invention can operatively take place according to the steps described in the following.

(61) At first, the bead breaking arm 7 is in a disengaged position, i.e. in a position of maximum distance from the frame 2 of the tyre changing machine 1, as illustrated in FIGS. 3 and 7b.

(62) In this position, the rod element 18 is in the completely open position, i.e. the position of maximum extension towards the outside of the tubular body 22, and the nut 30 is positioned in abutment with the sleeve 25.

(63) The effective opening of the bead breaking arm 7 will be decided as the operator desires, according to the size of the wheel R to be worked on.

(64) The lever L is in the rest position (FIG. 7a), and the Bowden cable 12 is not tensioned.

(65) The drive selector device 14 engages the first pulley 15 (FIG. 7c).

(66) The control and stop element 13 is maintained in a rest position (FIGS. 7d and 7e) by the helical spring 19, which overcomes the force exerted by the pusher element 20 via the abutment surface 210, due to the preload of the spring 20a.

(67) In this configuration the upper portion 13a of the control and stop element 13 is in a distanced position with respect to the rod element 18.

(68) With reference to FIG. 8a, when the operator rotates the handle M of the lever L in the clockwise direction, the Bowden cable 12 is tensioned, i.e. pulled, along the longitudinal axis of the bead breaking arm 7, towards the bead breaking tool 8, thanks to the action of the movable block B.

(69) At the same time at the moment that the handle M is rotated, as illustrated in FIG. 8a, the movable block B activates a button of the microswitch type (not illustrated) which sends a switching-on command to the electric motor 10.

(70) With reference to FIG. 8c, the control and stop element 13 is displaced by the action of the Bowden cable 12 towards the left, i.e. towards the position of the endless screw 24. The control rod 17 will also be subject to a displacement towards the left (still with reference to FIG. 8c), bringing the drive selector device 14 to decouple from the first pulley 15 and enmesh on the second pulley 16, so that the electric motor 10 can transmit the drive, via the second belt 160, to the pulley 21 associated to the bead breaking arm. Said pulley 21 sets the tubular body 22 and therefore the endless screw 24 in rotation which, in turn, imparts an axial translational motion, in a screwing direction, on the rod element 18, which, by sliding freely internally of the sleeve 25, will begin to return internally of the tubular body 22, gradually leaving the initial position of maximum opening, illustrated in FIG. 8b.

(71) By the action of the nut 30 on the sleeve 25 or directly on the bead breaking arm 7, the traction force will be transmitted from the rod element 18 to the bead breaking arm 7, which will therefore begin to gradually move towards the frame 2 of the tyre changing machine 2.

(72) With reference to FIGS. 8d and 8e, the control and stop element 13 also starts moving towards the left i.e. towards the endless screw 24, overcoming the resistant force of the helical spring 19, in doing this making use of the contribution of the pusher element 20, preloaded by the spring 20a. The upper portion 13a of the control and stop element 13 begins to lower, pushed by the abutment surface 210 of the pusher element 20, and thus nears the rod element 18.

(73) With reference to FIG. 8f, an intermediate position of the rod element 18 is illustrated, i.e. a position partially retracted internally of the tubular body 22. The force of the helical spring 19 has been completely overcome and the spring can also be in a distal position with respect to the control and stop element 13, which in turn will be newly neared to the rod element, up to reaching an operating position; the upper portion 13a of the control and stop element 13 is at a lower height than the external diameter of the first sub-portion 321 of the smooth portion 18b of the rod element, though without coming into contact therewith. This is possible because in the configuration illustrated in FIG. 8f, the shoulder 32 (not visible in the figure) fashioned on the rod element 18 is now on the left with respect to the control and stop element 13, which thus directly faces, though without coming into contact therewith, on the second sub-portion 322 of the smooth portion 18b of the rod element 18, i.e. at the flat surface 320.

(74) With reference to FIG. 9a, the bead breaking arm 7 is in the working position, with the rod element 18 in the completely closed position, i.e. substantially retracted internally of the tubular body 22 (FIG. 9b).

(75) With reference to FIG. 9c, the control and stop element 13 is maintained in an operating position, i.e. completely displaced to the left in the drawing, i.e. towards the endless screw 24. In this configuration the upper portion 13a of the control and stop element 13, by action of the pusher element 20, is in a maximum neared position, i.e. in the operating position, towards the rod element 18.

(76) In the above configuration, the bead breaking arm 7 is therefore in the working position, and the bead breaking tool 8 has already been able to engage on a tyre P and cause the detachment of at least a portion of the bead of the rim C of a wheel R previously and advantageously positioned by an operator.

(77) In this position, the electric motor 10 continues to function, however the screw/nut coupling between the endless screw 24 and the threaded portion of the rod element 18 is such that the rod element 18 remains substantially stationary in the closed position i.e. the maximum screwed position. In a case of eventual small residual axial displacements, in every case they can be advantageously damped by appropriate elastic means 34 positioned internally of the tubular body 22, for example at the pulley 21.

(78) The tyre changing machine 1 of the present invention can possibly be advantageously provided with an electronic control system, which can comprise a safety device adapted to switch off the electric motor 10 after a predetermined operating time, with the rod element 18 in the completely closed configuration.

(79) Once the bead breaking of the at least a portion of bead has been obtained, the operator simply releases the handle M, which, recalled by appropriate elastic means (not illustrated), rotates in an anti-clockwise direction and returns into the initial position thereof, imparting a like movement on the movable block B solidly constrained to the lever L. This means that the Bowden cable 12 is no longer subjected to tension.

(80) On release of the microswitch previously activated by the block B, the electric motor 10 is automatically activated by the electronic control system, setting the drive shaft 10a in rotation in the opposite direction, i.e. the unscrewing direction, with respect to the preceding screwing direction of the rod element 18 on the endless screw 24.

(81) The enmeshing of the first threads of the screw/nut couple can be facilitated by the action of the elastic means 34.

(82) The control and stop element 13 remains substantially in the same operating position, while the rod element 18 translates axially towards the right, i.e. towards the maximum opening position.

(83) Any counter-rotations of the rod element 18 are prevented by the presence of the flange 31, which interacts with the second sub-portion 322 of the smooth portion 18b of the rod element. During the translation movement in the opening direction of the rod element 18, the bead breaking arm 7 is stationary in the closed position, i.e. in the proximal position with respect to the frame 2 of the tyre changing machine 1, since the nut 30 no longer engages the sleeve 25 and the rod element 18, by sliding freely internally of the sleeve 25, is no longer able to transmit any force to the bead breaking arm 7.

(84) The operator can therefore manually open the bead breaking arm 7 as desired, using the lever L without rotating it, with the desired velocity. In this step, the nut 30 assumes a simple end-run function for the purposes of safety, in order to guarantee that the open position of the bead breaking arm 7 does not assume excessive distances from the frame 2 of the machine 1.

(85) Clearly the travel of the rod element 18 is linked to the length of the threaded portion 18a which can be chosen as desired during the design stage, in order to guarantee full operativity of the bead breaking assembly with wheels of any dimension. In a similar way, the velocity of screwing and unscrewing of the rod element 18 on the endless screw 24 is a function of their specific size and the rotation velocity of the drive shaft 10a, as well as the dimensioning of the belt and pulley transmission system. All of these variables are preferably selected in such a way as to obtain an optimal velocity, both in terms of productivity and safety for the operator, and a safeguarding of the wheel to be worked on.

(86) During the opening motion thereof, when the rod element 18 is close to the maximum open position, at a certain point the washer 33 again pushes the helical spring 19 against the control and stop element 13, which will be pushed to the right, and the upper portion 13a will begin to contact the pusher element 20 at the abutment surface 210. In case, the upper portion 13a might also be accompanied, during this step of returning towards the rest position, by the action of the shoulder 32 thereon.

(87) Once the maximum opening position of the rod element 18 has been reached, the control and stop element 13 will return to the initial rest position, consequently displacing also the control rod 17 in the initial position thereof, which leads to the disengagement of the drive selector device 14 from the second pulley 16 and enmeshing thereof on the first pulley 15.

(88) In order to prevent an unexpected and undesired rotation of the wheel support assembly 6, the stem 220 of the pusher element can be dimensioned so as to come into contact, in that working configuration, with a control device, for example of the microswitch type, for automatically controlling the switching-off of the motor on conclusion of the translational opening motion of the rod element. The microswitch device (not illustrated in the figures) can usefully be mounted solidly to the frame 2 of the tyre changing machine 1.

(89) Once this operating cycle has concluded, the operator can therefore manually completely open the bead breaking arm 7 which, by means of the sleeve 25, is as mentioned free to slide along the rod element 18, and eventually to advantageously position the wheel R in such a way as to carry out the bead breaking operation of a further portion of bead of the tyre P.

(90) This operation can obviously be repeated more than once, up to obtaining the complete debeading of the tyre P from the rim C.

(91) The embodiment described above is obviously provided merely by way of non-limiting example and a person skilled in the art can obviously conceive further embodiments of the present invention, all falling within the scope of protection of the appended claims.

REFERENCE LIST

(92) 1 tyre changing machine

(93) 2 frame

(94) 3 support post

(95) 4 mounting/demounting means

(96) 5 mounting/demounting tool

(97) A rest surface

(98) 6 wheel support assembly

(99) R wheel

(100) C rim

(101) P tyre

(102) 7 bead breaking arm

(103) 7a intermediate arm

(104) 8 bead breaking tool

(105) 9 opposing surface

(106) 10 electric motor

(107) 10a output drive shaft

(108) 11 selective drive transmission means

(109) F control pedal

(110) L control lever

(111) M handle of the lever

(112) B movable block

(113) 12 Bowden cable

(114) 13 control and stop element

(115) 13 upper portion of the control and stop element

(116) 14 drive selector device

(117) 15 first pulley

(118) 16 second pulley

(119) 150 first belt

(120) 160 second belt

(121) 17 control rod

(122) 18 rod element

(123) 18a screw-shaped control portion of the rod element

(124) 18b smooth portion of the rod element

(125) 320 flat surface

(126) 321 first sub-portion of the smooth portion

(127) 322 second sub-portion of the smooth portion

(128) 19 helical spring

(129) 20 pusher element

(130) 20a preload spring

(131) 210 abutment surface

(132) 220 stem

(133) 21 pulley solidly mounted to the tubular body

(134) 22 tubular body

(135) 23 support tube

(136) 24 endless screw

(137) 25 connecting means

(138) 26, 27 pins

(139) 28, 29 slots

(140) 30 striker element

(141) 31 flange

(142) 32 shoulder fashioned on the rod element

(143) 33 washer

(144) 34 elastic means